Nitrogen and Phosphorus Mineralization

By Jared L. DeForest

Procedure

Initial Nitrogen (Day 0)

In a 50 ml centrifuge tube

• 10 g Field fresh soil
• 20 ml 1 M KCl (74.59 g KCl/liter)

Place on orbital shaker for one (1) hour.

Centrifuge and decant into a 15 ml centrifuge tube.

Measure NH₄⁺ and NO₃ using colorimetric methods within a week.

Initial Phosphorus (Day 0)

In a 50 ml centrifuge tube (if available, Oakridge tubes)

• 10 g Field fresh soil
• 1 Bicarb charged AEM resin strip (Charging: shake strips 10 minutes in 100 ml 0.5 M NaHCO₃, rinse 3 times with DI water, shake dry)
• 20 ml DI water

Shake for 4 hours, centrifuge, and discard supernatant

In a 250 ml flask

• 1 AEM strip
• Extract resin with 25 ml of 0.5 M HCl (41.7 ml 12M HCl/liter) for 18 hour on a shaker.

Measure Resin P using the ascorbic acid colorimetric method within a day.

Incubated N and P (Day 14)

In a 125 ml sample cup

• 20 g Field fresh soil

Loosely put on the lid.

Place in the incubator at 25°C for around two (2) weeks.

Check moisture every week. If dry, then spray once with distilled water.

In 14 days (two weeks)

In a 50 ml centrifuge tube (if available, Oakridge tubes)

• 10 g Soil for P analysis from the incubated soil
• Label “incubated”

Repeat procedure P procedure from above.

In the incubated 125 ml sample cup

• 10 g Remaining soil for N analysis
• 20 ml 1 M KCl
• Label “incubated”

Repeat procedure N procedure from above.

Created: 02/02/11